body {
    /* background-color:salmon; */
}
#title{
    width: 450px;
    height: 70px;
    margin: 0 auto;
    text-align: center;
    font-size: 30px;


}
.box{
     display: flex;/* 弹性的盒子 */
     flex-direction: row;/*横排*/
     justify-content: center;

}
.cla{
    height: 300px;
    width: 30%;
    border-style: solid;
    margin: 1PX 1PX;

}
